42 lines
1.3 KiB
JavaScript
42 lines
1.3 KiB
JavaScript
import _curry2 from "./internal/_curry2.js";
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/**
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* Builds a list from a seed value. Accepts an iterator function, which returns
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* either false to stop iteration or an array of length 2 containing the value
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* to add to the resulting list and the seed to be used in the next call to the
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* iterator function.
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*
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* The iterator function receives one argument: *(seed)*.
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*
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* @func
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* @memberOf R
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* @since v0.10.0
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* @category List
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* @sig (a -> [b]) -> * -> [b]
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* @param {Function} fn The iterator function. receives one argument, `seed`, and returns
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* either false to quit iteration or an array of length two to proceed. The element
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* at index 0 of this array will be added to the resulting array, and the element
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* at index 1 will be passed to the next call to `fn`.
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* @param {*} seed The seed value.
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* @return {Array} The final list.
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* @example
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*
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* const f = n => n > 50 ? false : [-n, n + 10];
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* R.unfold(f, 10); //=> [-10, -20, -30, -40, -50]
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* @symb R.unfold(f, x) = [f(x)[0], f(f(x)[1])[0], f(f(f(x)[1])[1])[0], ...]
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*/
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var unfold =
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/*#__PURE__*/
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_curry2(function unfold(fn, seed) {
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var pair = fn(seed);
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var result = [];
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while (pair && pair.length) {
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result[result.length] = pair[0];
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pair = fn(pair[1]);
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}
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return result;
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});
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export default unfold; |